Bulk density is one of the most important parameters in reservoir evaluation. It is widely used for estimation of reserves of hydrocarbons in reservoirs. Traditionally, well logs and core measurements are the two approaches to obtain key petrophysical parameters for reservoir evaluation and description. These measurements are expensive and many times they require extra rig time, which is also very expensive.
For example, bulk density can be measured in real time with logging while drilling (LWD) density log or can be measured using wireline (WL) density log. Both use a gamma ray source and measure the attenuated gamma ray coming to the detector after interacting with the formation. Generally speaking, the LWD density measurement represents the bulk density of the rock with the formation fluids in the pore space, whereas the WL density measures the bulk density of the rock with invaded fluids; for low permeable unconventional rocks, the difference should be minimal. Bulk density can be precisely measured using core plugs when they are available.
Obtaining accurate petrophysical parameters from drill cuttings is beneficial and desirable for at least two reasons. First, drill cuttings are readily available from any drilled well and thus does not add extra rig time or extra cost to the operation. Second, measurement can be done at the wellsite and offers data for real-time operational decisions, such as drilling and the succeeding hydraulic fracturing.
However, it is a challenge to measure the volume of the cutting accurately as it is hard to remove the fluid on the surface of the cutting. The traditional sample preparation method uses a damp paper towel to remove the excess fluid from the surface, and due to the irregular shape of the surface features, the validity of the total removal of the surface fluid is always questionable. Moreover, if the paper towel is too dry, the fluid within the cutting sample can be lost due to capillary force.